1. Field
The present disclosure relates to a gas separation membrane and a method of preparing the same, and more particularly, to a gas separation membrane that has a high gas permeation rate and excellent selectivity and processability.
2. Description of the Related Art
Gas separation processes include membrane separation processes, pressure swing adsorption (PSA) processes, cryogenic processes, and the like. PSA and cryogenic processes, the designs and operations of which have been developed, are technologies currently in common use, while gas separation using membrane separation is relatively new.
A gas separation processes using a polymer membrane has been commercialized with a gas separation membrane module in the “Prism” product by Monsanto Co. in 1977. The system is relatively low in energy consumption, provides for reduced investment in plant and equipment costs compared to existing methods, and it has an increasing annual share in the gas separation market.
Gas separation membrane materials used so far are largely organic polymers, including polysulfone, polycarbonate, polypyrrolones, polyarylate, cellulose acetate, polyimide, and the like. Although some polymer materials show high separation efficiency with respect to specific gas mixtures, most polymer materials have seen very limited application because of their high cost and difficulties in manufacturing separation membranes in a form suitable for industrial use, for example, in the form of a planar thin film sheet or a hollow thread.
In general, natural and synthetic polymer gas separation membranes in the form of a dense solid phase structure (such as planar membrane, composite membrane, or a hollow thread) may exhibit high selectivity with respect to gas mixtures, and have been manufactured largely as an asymmetric membrane with a thin selective separation layer on a porous support to increase the gas permeation rate.
For example, a gas separation membrane having a carbon molecular sieve (CMS) active layer on a metal or ceramic porous support is known as a membrane having a selective permeability.
The gas separation membrane having a CMS active layer may be used in gas separation, precision filtration, or ultrafiltration and is prepared by thermal decomposition of polymers at a temperature of 600° C. or higher. The high decomposition temperature results in manufacturing processes that are energy intensive and complicated, and due to a different coefficient of thermal expansion with the metal or ceramic porous support, cracks or pinholes are formed in the CMS active layer, and thus efficiency of such a gas separation membrane may be decreased. FIG. 1 schematically illustrates a cross-section of a prior art gas separation membrane. As shown in FIG. 1, a plurality of cracks and pinholes 13 are formed in a CMS active layer 12, which is formed on a metal or ceramic porous support 11. As a result, selectivity for gas significantly drops due to the cracks and pinholes 13 formed on the CMS active layer 12.
Therefore there remains a need for an improved gas separation membrane.